Variable thickness wet film applicator



Dec. 17, 1963 s. A. KOTELES EI'AL 4,

VARIABLE THICKNESS, FILM APPLICATOR Filed July 25, 1962 MENTOR-9- firmlz/v A, KoreLes BY CH4EL5 J. 5%

United States Patent 3 114,165 VAREAELE THICKNESS WET FILM APPLICATOR Stephen A. Koteles, Maple Heights, Ohio, and Charles J. B er-g, (lahiawn, llh, assignors to The Sherwindi'rlhams Company, Cleveiand, Ohio, a corporation of (line Filed July 25, 1952, Ser. No. 212,261 1 tllaim. (Cl. 236) This invention relates to improvements in variable thickness wet film applicators.

Devices for casting wet films of predetermined thickness have particular utility in the testing, analysis and/ or quality control of coating compositions. Thus, certain properties of various fluids such as paints and the like may be determined by observation and analysis of films of such materials under both wet and dry conditions. A conventional device of this type known as a draw down bar has been employed for the deposition of such films. In use, a Wedge of the coating composition undergoing test is placed in the nip formed between a plane surface and the draw down bar which is then drawn over the plane surface to deposit a film of the coating composition thereon. Variations in the depths of such films have been attained heretofore by wrapping wires or hands about the bar thereby spacing the peripheral surface of the bar from the plane surface upon which the film is to be deposited. This requires a plurality or set of bars having different cross-sectional dimensions in relation to the effective cross-sectional dimension presented to the plane surface by the periphery of the wound Wire or band.

Briefly, in accordance with this invention, there is provided a single bar or film applicator capable of applying films of varying thickness simply by rotating the bar on its axis. The applicator has axially displaced circular cross sections of different diameter and disposed on parallel axes displaced from each other to present an effective cam surface. Suitable indicia are disposed on the surface in predetermined relation to selected circumferential points respectively to indicate the corresponding film thickness. Suitable dams may be formed in the surface of the applicator to confine the film fiuid to the applying surface.

In the drawings:

FIG. 1 is a plan view of a variable film thickness applicator in accordance herewith;

FIG. 2 is an enlarged view of a portion of the applicator of this invention showing the variable cross section and dams in greater detail;

FIG. 3 is a cross-sectional view taken along the lines 33 in FIG. 2;

FIG. 4 illustrates the manner in which the applicator of this invention is employed.

Referring now more particularly to FIG. 1 of the drawings, there is provided an elongated bar having extremities It? and 11 of circular cross section formed on a common central axis designated by the center line 12. The intermediate portion 13 of the bar is also of circular cross section of lesser diameter and formed about a central axis designated by the center line 14. Viewing FIG. 1 in conjunction with FIG. 3 of the drawings, the axis 14 is displaced from the axis 12 a radial distance no greater than and preferably less than the diiference in the diameters of the bar extremities and its intermediate portion.

As a consequence, when employed in the manner herec snares 1C6 Patented Dec. 17, 1953 tofore described to apply a film of coating composition to a plane surface as illustrated in FIG. 4 of the drawings, it is possible to apply films of different thickness merely by rotating the applicator bar about the common axis of its extremities. Further, in accordance with this invention, the plurality of indicia markings 15 may be etched or otherwise suitably disposed in circumferentially spaced relation about one or both extremities. The disposition of such indicia can be calibrated to visually indicate the variations in gap clearances that can be attained by various rotated positions of the bar relative to the plane surface. Such calibration is obtained by measuring the thickness corresponding to selected circumferential points and then placing a corresponding marking in predetermined relation to such selected circumferential point to visually indicate the gap clearance that will result. In the preferred embodiment, the markings are disposed on the surface of the extremity diametrically opposite from the selected circumferential point engaging the plane surface to which the film is being applied, thereby providing the operator with a visible indication of the film thickness being applied. The film thickness may vary from actual gap clearance because of viscosity, solids content, flow properties, etc., all of which can be predetermined and adjusted for in the actual testing of films. For exampie, if predetermination, e.g. as by a preliminary draw-down, indicates that in order to obtain a wet film 10 mils thick a wet film 20 mils thick must be cast, such allowance is made for the variation.

Still further in accordance with this invention, as best shown in FIG. 2 of the drawings, suitable dams l6 and 17 are formed on either side of the intermediate portion 13 of the applicator. These dams are formed by cutting an annular groove around the peripheral surface of each extremity of the bar adjacent its juncture with the working intermediate portion. Such grooves will operate during application of the film to confine the film fiuid therebetween and preferably within the working surface of the intermediate portion.

A specific example of a draw down bar embodying the principles of the present invention has extremities which are approximately in diameter, disposed at opposite ends of a bar which is 8 long. The extremities form handle portions which are each desirably 2" long. The intermediate portion under which the film of predetermined thickness passes is conveniently about 4 long and cut on a center which is displaced from the normal axis of the handle portions by an amount which is equal to about 0.010". By varying the diameter of the intermediate portion, gap clearances ranging from about 0.5 mil to as much as mils or more may be provided. As indicated above, suitable indicia are inscribed in one or both of the handle portions to indicate to the operator the gap clearance which is related to the thickness of the film being deposited.

While the variable thickness wet film applicator of this invention may be employed with any type of coating composition, it is particularly suitable for those coating compositions having rheological properties akin to viscous fiuids such as plastisols and the like. As a consequence hereof, there has been provided a single applicator capable of applying films of various thickness within a controlled area on a plane surface thereby enhancing the ability to examine and analyze the properties of the coating material as and for the purpose needed.

We claim:

A variable Wet film applicator consisting of an elongated drawdown bar having a circular cross section at its extremities each of which extremities defines a smooth cylindrical handle portion and has a common central axis with the other, the intermediate portion of said drawdown bar being integral therewith and having a circular cross section of lesser and axially uniform diameter on a central axis parallel to and displaced from the common axis oi 4 the extremities a distance no greater than the difierence in said diameters, and an annular groove encircling each extremity adjacent the intermediate portion and coacting therewith to confine the fluid between the grooves during application.

References Cited in the file of this patent UNITED STATES PATENTS 

